This invention relates generally to a disk-type record medium reproduction apparatus, and more particularly, to a pick-up moving mechanism which easily detects a position of the pick-up unit by reducing vibration of the pick-up unit caused by the presence of two gaps. The first gap is between the pick-up moving screw and the nut, and the second gap is, radially and axially of the screw, an engagement between the nut and a connecting member stemming from the body of a pick-up unit.
Generally, in the disk-type record medium reproduction apparatus, information recorded on the disk-type record medium such as Compact Disk (CD) is reproduced by rotating the record medium, irradiating the recorded side of the record medium with a laser, and reading the reflected light from the recorded side.
In the mechanical operation, the angle of inclination of the object lens is consequently changed with the fixing of the pick-up unit and the irradiating direction of the laser is consequently moved outward from the record medium, thereby allowing the reading of the reflected light. The pick-up unit is moved outwardly with the pitch moving everytime the amount of movement reaches a predetermined value, for example, 0.5 mm. Such operation then is repeated. When pitch moving the pick-up unit, the object lens detects position information from the pick-up unit with high speed movement. At the same time, the pick-up unit is moved forwardly or rearwardly and severely or finely so as to reach next position. Accordingly, the object lens must be carefully attached to the pick-up unit to allow for precise movement.
In a conventional pick-up moving mechanism, such as the kind of the reproduction apparatus, shown in FIG. 24 and FIG. 25, a nut c is attached to part of pick-up unit b which is threadedly engaged on pick-up moving screw a. Pick-up unit b is moved via linear guide rod e by rotating pick-up moving screw a from motor d. Nut c is engaged to connecting member g stemming from body f of pick-up unit b. It is very difficult to assemble and obtain an accuracy of parallelism between guide rod e and pick-up moving screw a.
Accordingly, there is a slight gap h.sub.1 in the direction of rotation of pick up moving screw a between connecting member g and nut c so as not to negatively effect the accuracy of positioning of pick-up unit b and not obtain a high accuracy of parallelism. There is also another gap h.sub.2 in the axial direction of moving screw a.
If the motor d is repeatedly rotated in both directions severely or finely so as to detect the position of pick-up unit b, nut c vibrates severely in same direction since there are slight gaps h.sub.1 and h.sub.2 between connecting member g and nut c. Such vibration makes nut c strike against connecting member g. A shock induced by such strike is transferred to body f of pick-up unit b.
As a result, the object lens attached to the pick-up unit responds sensitively to severe vibration. Accordingly, the prior art mechanisms have the problems of taking too much time to respond or the inability to accurately read the recording side. The subject invention provides a solution to these problems.